1. Field of the Invention
The present invention relates to a cylinder injection type fuel injection valve to be attached to a cylinder head in order to directly inject fuel into a combustion chamber in an internal combustion engine.
2. Discussion of Background
A conventional cylinder injection type fuel injection valve 20 has such a structure of a combination of an injection valve body 22 with a needle valve 21 and a solenoid 23 for operating the needle valve 21 as shown in FIG. 4, for instance. The solenoid 23 comprises a housing 24, a core 25, a coil assembly 26, a ring 27 made of a thermoset resin, O-rings 28, 29 of an elastic material, a spacer 30 and an armature 31.
Sealing for fuel between the inner periphery of the ring 27 and the outer periphery of the core 25 and between the outer periphery of the ring 27 and the inner periphery of the housing 24 are maintained by means of the O-rings 28, 29 made of an elastic material. The above-mentioned structure minimizes occurrence of the destruction of sealing for fuel, even in a case that heat is abnormally generated due to a supply of an overcurrent to the coil assembly 26, because the ring 27 is made of a thermoset resin whereby deformation of the ring 27 is prevented.
The above-mentioned cylinder injection type fuel injection valve 20 for directly injecting fuel into a fuel chamber is fixed to a cylinder head 32 in an internal combustion engine in such a manner that an outer circumferential portion 24a at a lower part of a flange 33 of the housing 24 is inserted in a fitting opening 32a in the cylinder head 32, and fixing is effected in the axial direction of the injection valve by fitting metallic members from an upper direction of the flange 33. A fuel supply tube 34 is fixed to the cylinder injection type fuel injection valve 20 by fitting a fitting opening 34a to an upper part of the injection valve 20 by interposing an O-ring 35 for-sealing the upper part of the injection valve 20 after the injection valve 20 has been fixed to the cylinder head 32.
In the conventional cylinder injection type fuel injection valve having the above-mentioned construction in which the fuel supply tube 34 is connected to the injection valve 20, there was a problem as follows. Looseness in fitting between the fuel supply tube 34 and the cylinder head 32, and scattering in dimensions of fitting openings 32a, 34a of the cylinder head 32 and the fuel supply tube 34 might result a misalignment of axis between the fitting openings 32a and 34a whereby a bending load was applied to a portion of the lower part of the flange 33 of the injection valve and a part to which the O-ring 35 was fitted. The application of the bending load increased an inclination angle of the core because the ring 27 was made of a resinous material. As a result, there was a change of a magnetic circuit formed in the injection valve, and a flow rate was changed.
FIG. 5 is a diagram showing a state that a load is applied to the injection valve which have been fixed to the cylinder head 32 wherein an arrow mark C indicates a force applied to the injection valve in which the axial center of the fitting opening 32a deviates from the axial center of fitting opening 34a.
FIG. 6 is a diagram showing a state that the core 25 is inclined due to the load applied so that an air gap formed between the core 25 and the armature 31 is ununiform. When the core 25 receives a load D through the O-ring 35, the core 25 is inclined around a fulcrum point as a fastening portion E between the core 25 and the housing 24.
In the cylinder injection type fuel injection valve 20 attached to the cylinder head 32 of an internal combustion engine to directly inject fuel into a combustion chamber, it is necessary that the solenoid 23 generates a large electromagnetic attractive force in order to open quickly the needle valve 21 because a high fuel pressure is applied to the inside of the injection valve.
In the conventional cylinder injection type fuel injection valve, however, it was necessary to use the ring 27 having a large wall thickness F, as shown in FIG. 7, in order to maintain a fracture strength to a high fuel pressure because the ring 27 was made of a thermoset resin. Specifically, it was necessary that the wall thickness F was 1.5 mm or more, in considering scattering in dimensions of the ring formed by molding resin, in order to assure a sufficient strength under a fuel pressure of 8 MPa. This inevitably made the distance between the coil 36 and the air gap portion g longer and increased the number of magnetic fluxes which do not pass through the air gap portion g among magnetic fluxes produced in the coil 36, whereby a sufficient electromagnetic attractive force could not be obtained.